The present invention relates generally to three-phase alternating current (AC) circuits and, more particularly, to a system and method for detecting and localizing excess voltage drop in single or multiple phases of three-phase AC circuits.
In industrial facilities, electrical machines such as generators, AC motors, and/or transformers are used in various applications. As one example, induction motors are used for applications like pumping, cooling, material movement, and other applications where cost-efficient and robust motors are required. An electrical distribution system is used in conjunction with electrical machines in such applications, with the electrical distribution system including protection and control components such as breakers, contactors, starters, etc.
In providing connections within an electrical distribution system and at the electrical machine, it is recognized that an improper connection of protection and/or control components can lead to over-heated contacts that can lead to fire, equipment damage, and process downtime and efficiency loss. That is, excess voltage drops can occur in distribution circuits when electrical connections become loose or have less wire binding force. While even good joints/connections have some level of voltage drop (e.g., in the range of 3-10 mV) that is acceptable, bad joints/connections have an excess voltage drop in the range 100-300 mV or higher. Such voltage drops can lead to abnormal power dissipation at the connections and correspondingly to over-heated contacts or hot spots in the connections that can initiate fire and equipment damage. Even at an early stage, the voltage drops lead to energy losses as line drops, in effect reducing motor efficiency and motor life for example.
Often, the problem of improper electrical connections is addressed to a certain extent by performing preventative maintenance, like annual retorquing of connections or by periodic inspection of all the electrical connections when the distribution circuit is offline. With respect to inspection of the electrical connections, such inspections are typically performed via separate dedicated sensing devices that inspect the electrical distribution system using acoustic or temperature sensing. For example, infrared (IR) scanners are often used to perform a periodic thermal inspection of the electrical distribution system. While effective, the inspection of electrical distribution system by way of such IR scanners is an intensive procedure that can be quite costly. Additionally, the inspection of an electrical distribution system by way of an IR scanner does not provide for online monitoring of the electrical connections and are limited to line-of-sight monitoring.
It would therefore be desirable to provide a system and method that detects excess voltage drops in a distribution circuit in an efficient and cost effective manner, so as to identify improper electrical connections in the circuit. It would also be desirable for such a system and method to be non-intrusive, such that the detection of excess voltage drops in a distribution circuit can be performed while the circuit is online. It would still further be desirable for such a system and method to localize a detected excess voltage drops to a particular phase or phases of the distribution circuit and quantify the excess drop.